Effect of N-α Substitution on the Electropolymerization of N-Substituted Pyrroles: Structure-Reactivity Relationship Studies

Structure reactivity relationship (SRR) studies to understand the effect of N-alpha substitution toward electroactive poly(pyrrole) film formation have carefully been performed. To conduct these SRR studies, a selected chemical library of 21 different N-substituted pyrrole derivatives has been developed using the key well-known Clauson-Kass synthetic reaction from corresponding amine precursors. While investigating electropolymerization features of these novel N-substituted pyrroles, we observed that the steric factor due to alpha-substitution, one among other factors, plays the most significant role in preventing electropolymerization of these oxidizable chemical species. Interestingly, even a sterically small chemical group like a CH3 one present at alpha-position is large enough to prevent monomer electropolymerization. Density functional theory calculations were carried out to analyze the polymerization of substituted pyrrole molecules and to understand the effect of N-substituents on electropolymerization toward the formation of functional conductive film. This systematic study paves the way to effectively design the right N-substitution for the obtainment of corresponding modified functional electrodes for further related applications.